1. Field of the Invention
This invention relates generally to a method and apparatus for revascularization of a heart, and more particularly to a method and apparatus for revascularization using laser outputs.
2. Description of Related Art
Heart disease is a significant health problem which has been the subject of substantial medical study. By-pass surgery has become commonplace, yet such surgery may only partially correct a diminished blood supply to heart muscle and may be unavailable to many patients, either because of the nature of the occlusions or the physical condition of the patient.
One promising alternative or adjunctive technique for treating such cases is known as transmyocardial revascularization (TMR). This technique was considered in the work of Dr. C. Beck in "the Development of a New Blood Supply to the Heart by Operation," Annals of Surgery Annals of Surgery, Vol. 102, No. 5 (11/35) pp. 801-813. The method was also studied in the work of Dr. M. Mirhoseini and M. Cayton, an example of which is found in "Lasers and Cardiothoracic Surgery" in Lasers in General Surgery (Williams and Williams, 1989) pp. 216-223. A device to perform TMR is described in Aita et al., U.S. Pat. No. 5,380,316, issued Jan. 10, 1995. In TMR generally the surgeon creates narrow channels in the heart at the surface of a ventricle of the heart. The surgeon generally uses a laser to create these channels either by accessing the endocardium through a percutaneous route or the epicardium through an incision in the chest wall. The pressure within the left ventricle during systole forces oxygenated blood into the channels and consequently oxygenates the ischemic myocardium of the left ventricle.
It is desirable to be able to control the time point within the cycle of heartbeats at which the heart is revascularized. A heart synchronized pulse laser system which operates on a beating heart between the R and T waves of the electrocardiogram (ECG) signal is described in U.S. Pat. No. 5,125,926 (Rudko).
An electrocardiogram signal may not always provide the most accurate indication of heart function. Further, the electrocardiogram signal is a passive indication of heart rate. It is not a method to control the rate at which the heart beats.
There is a need for an apparatus for stimulating revascularization of the heart or creating channels in the heart where the revascularization event caused by the revascularization device can occur at a selected time in relation to the heartbeat. There is a further need for an apparatus for treating a heart by stimulating revascularization of the heart or creating channels in the heart where the device can control the heartbeat rate. There is further need to reduce the number of cycles over which a laser must be fired to achieve the desired depth of channels in the heart.